This invention relates to a process for removing organic and inorganic contaminants from phenolic stripped sour water. More particularly, this invention is directed to a process for removing inorganic contaminants such as selenium from phenolic stripped sour water employing reverse osmosis and appropriate pH adjustments.
A refinery wastewater stream in a refinery wastewater treatment unit is typically formed from the combination of wastewater streams present within the refinery unit. The refinery wastewater stream will ordinarily contain many regulated organic and inorganic contaminants present therein which can be recognized as a biological and health hazard. Standards promulgated by federal and state agencies restricting the amount of the contaminants and, in particular, the amount of selenium, present in the refinery wastewater stream prior to the stream being disposed into publicly owned treatment works or discharged into waste injection wells have been imposed.
Phenolic stripped sour water is one such wastewater stream present within the refinery unit used to form the refinery wastewater stream. The sour water typically has a high content of selenium, e.g., of up to at least 65 percent of the total selenium content present within the refinery wastewater stream. Processes for removing selenium from wastewater streams have been employed. See, e.g., U.S. Pat. Nos. 4,678,584; 4,915,928; 4,971,702; 5,322,600; 5,453,201; 5,591,346 and U.S. Pat. No. 5,603,838. However, since the greatest concentration of selenium is in the phenolic stripped sour water, processes for reducing the concentration of selenium in phenolic stripped sour water need to be employed to reduce the amount of selenium in the sour water prior to it being combined with the other wastewater streams to form the refinery wastewater stream.